Vaginas

I wouldn't normally do this but I'm worried (I'm 15 years old) I have had a normal vagina with no problems so far untill yesterday when it got very itchy and sore so I decided to see if there was anything wrong down there ( using a mirror) and when I touched my vagina it got an intense stinging/burning feeling. At first I thought it might be a STI but I realised it couldn't be as I am still a virgin. Can someone help as I have no idea what is wrong ? The stinging/burning is still continuing now the next day it is also very red what could be wrong ?